1. Field of the Invention
The present invention is concerned with a boiler feed water deaerator having substantially vibration-free valve assemblies which give long-lived and trouble-free use. More particularly, it is concerned with such a deaerator wherein valve vibrations are reduced by virtue of an elongated, generally tubular, open ended valve shield for each valve configured to protect the movable components of the valve and reduce turbulence by directing water flow therethrough in a generally axial direction.
2. Description of the Prior Art
Corrosion in boiler equipment is caused by the presence of non-condensible gases such as oxygen and carbon dioxide, and by low pH values. The pH of boiler water can be raised chemically, but gases therein must be removed mechanically. Modern day high pressure boiler cycles have increased the need to protect the boiler components from corrosion. Indeed, a power plant boiler would deteriorate rapidly from the ravages of corrosion if non-condensible corrosion causing gases were not removed.
One established technique for deaeration of boiler water involves the use of a two-stage spray deaerator. In the first stage, incoming water flows from an inlet into an upper water box and thence through spray valves into a steam filled vented condensing chamber as thin walled, hollow cone spray patterns. The sprayed water then is dispersed in tray-type fill structure, and is collected in a lowermost basin. Latent heat transfer is essentially instantaneous because of the intimate water to steam exposure. As the water reaches the lower collection basin, at which point stage one is complete, water temperatures are within 2.degree. F. of the counterflowing saturated steam temperature, and virtually all dissolved oxygen and free carbon dioxide have been separated from the water. The oxygen and carbon dioxide are carried by a small amount of uncondensed steam out through the vent, exiting as a plume.
In the second stage, the water flows to a scrubber section where it is turbulated in intimate contact with the counterflowing steam scrubbing out the last remaining quantity of non-condensibles. The water simultaneously falls into storage, in a heated and completely deaerated condition.
In the above type of deaeration device experience has demonstrated that removal of oxygen and other corrosion causing gases is maximized where, in the first stage, the liquid is sprayed in thin films in an essentially cone-type pattern. For this purpose, specific types of spray valves have been developed. One such valve which has enjoyed considerable commercial success employs a flanged, centrally apertured body with a shiftable, frustospherical valve plug located and supported for movement relative to the valve body. The valve opens under the influence of water pressure, and serves to create the fine cone-like spray desired for optimum deaeration.
In certain instances valves of the type described are subjected to rather severe vibrations which can shorten valve life. It has been discovered that, by virtue of the horizontal component of incoming water in such a unit, the valve structures are subjected to lateral 1oads tending to displace the valve and lead to undue vibrations or chattering of the movable valve components against the rigid body thereof. Moreover, as the water passes through the valve, turbulent flow patterns tend to create additional undesirable vibrations. The overall result of these forces is to substantially lessen valve life and to deleteriously alter the performance characteristics thereof.